A portable terminal, such as a smart phone, an Internet device, and a portable game device, requires a slimmer appearance in order to improve portability for a user.
The portable terminals have limited sizes to be inconvenient to perform a user desired function by using a menu key, a number key, and a direction key, so that the portable terminal is currently configured so as to enable a user to directly select a menu item displayed on a screen by using a touch screen while the user views a screen.
The touch screen enables a user to touch a menu item displayed on a screen while viewing the screen to perform a desired function, so that the touch screen needs to be formed of a transparent material, and includes a touch electrode for detecting a touch input of the user.
The touch electrode is generally formed of two electrode lines having a crossing structure in the touch screen, and the two touch electrode lines may be formed in separate sheets, or in one sheet to determine a touch input of a user.
A touch screen having a lattice structure adopts a capacitive method, and a sensor electrode pattern is formed of a plurality of crossing first conductive-side lines and second conductive-side lines. When a touch object approaches the touch screen having the lattice structure, the first and second conductive-side lines, which are connected horizontally and vertically to each other, collect capacitance changed at the approaching point, and the touch screen analyzes a collected signal and detects a touch input.
An electrode of the touch screen adopts a transparent metal oxide, such as an indium tin oxide (ITO) having higher electric resistance than that of a conductive metal, but having high optical transmittance.
The transparent metal oxide does not have a problem in a device having a small surface area. Because a work function is large, and electric conductivity is not relatively high, there is a disadvantage in that when the surface area is increased, a voltage drop is generated.
When the transparent metal oxide is formed on a transparent film, such as a PET film, surface damage to a film is generated in proportion to a deposition time, and anion impact is generated, so that it is difficult to make a large touch screen.
In order to overcome the problem, US Patent Publication No. 2010-0156840 discloses a touch screen sensor for detecting a touch input by using a touch electrode having a mesh structure.
However, the touch electrode having the mesh structure may be visually recognized, or a Moiré effect may be exhibited by the mesh pattern.
When a line width of the touch electrode having the mesh structure is decreased, visual recognition and the Moiré effect are decreased, but there is a limit in an implementable line width of a micro pattern, and a method of implementing an ultrafine mesh structure having a line width in a submicrometer scale, which is less than 1 μm, has large processing cost, so that there is a problem in mass manufacturing and making the touch electrode large.
Accordingly, research on a reasonable manufacturing method capable of implementing an ultrafine mesh structure having a line width in a submicrometer scale, which is less than 1 μm, is demanded.